Since the introduction of plastic pipe, applications have been discovered which require a slit through the wall thickness of generally cylindrical plastic pipe. Cylindrical plastic pipes having an inner diameter and an outer diameter have been slit longitudinally so as to allow the plastic pipe to be flexed open and wrapped around, for example, another generally cylindrical pipe for which it is desired to provide insulation and/or protection. In this application the slit along the length of the pipe is generally made so as to cut through the minimum thickness of pipe wall required to achieve access to the inner surface of the pipe i.e., with reference to a cross-section of the slitted pipe, the slit is in alignment with a radius of the pipe.
While the slit aligned with the radius of the pipe is effective for applications such as providing a cover or insulation for another pipe, when the pipe to be protected has an outside diameter essentially equal to the inside diameter of the protective pipe, this radially aligned slit has certain drawbacks. For example, any expansion of the outside diameter of the protected pipe will cause a gap to appear along the radially aligned slit cut in the protective pipe.
In other applications for use of plastic pipe, expansion of the plastic pipe is required. For example, it is known to utilize relatively short lengths of slitted plastic pipe as insert sleeves to anchor bolts in certain materials such as cement, ceramics, or rock. In this application the slitted pipe may be sized for closely receiving a screw in the bore of the pipe. As the screw is advanced, threads are cut into the interior wall of the plastic pipe, thus forcing expansion of the sleeve into contact with the interior walls of a predrilled hole in which the sleeve has been inserted.
Regardless of whether expansion of the slitted plastic pipe is desired or not, the gap created at the slit by expansion of an object within the slitted pipe can be detrimental by allowing the object within the slitted pipe to contact undesired fluids.
A pipe slit in such a manner that would allow for expansion of the pipe diameter of the slitted pipe without creating a gap at the slit would prove to be a useful article.
Accordingly it is an object of this invention to provide an improved method and apparatus for cutting a slit along the length of a generally cylindrical plastic pipe.
It is a further object of this invention to cut a longitudinal slit in a pipe which will allow a diametrical expansion of the slitted pipe without creating a gap at the slit.
It is still a further object of this invention to provide an improved protective cover for an object contained in the slitted pipe.